High-power semiconductor lasers are commonly used as optical pump source for pumping of optical amplifier, such as but not exclusively Erbium doped fiber amplifiers (EDFA) and optical fiber based Raman amplifiers. In order to be useful as an optical amplifier pump source, semiconductor laser pumps need to maintain a fixed lasing wavelength with variations in temperature, drive current and/or output power of the laser. For both “980 nm pump lasers” and “Raman pump lasers”, the wavelength is typically stabilized by an external fiber Bragg grating (FBG). FIG. 1 illustrates a typical configuration of a prior art semiconductor laser-based pump source 5 for pumping fiber-optic amplifiers. In this configuration, an output facet 12 of a Fabry-Perot type semiconductor laser 10 is coupled to an optical fiber pigtail 20 having a lensed proximal end, which includes an FBG 22 that is formed within the fiber at some distance along its length from the lensed laser-coupled proximal end of the fiber pigtail 20, typically from a few centimeters to about a meter. A back facet 11 of the laser 10 typically has a high-reflection HR coating, while the output facet 12 has a low-reflection (AR) coating to reduce, but typically not eliminate, reflection of the laser light 31 generated within the laser cavity back into the laser 10. The FBG 22 reflects a relatively small portion 35 of the output laser light 33 back into the laser 10 to provide a wavelength stabilization, with light 37 transmitted through the FBG forming the useful output of the laser pump device 5. Typically, the FBG 22 stabilizes or fixes the optical spectrum of the pump 5 at or near the Bragg wavelength of the FBG 22 within a few tenths of a nanometer.
However, this arrangement has certain drawbacks, which include the added cost of forming an FBG within the fiber pigtail of the pump, a limited effectiveness of the wavelength stabilization using the distant FBG, a dependence of the stabilization on the laser to fiber coupling efficiency, and added optical loss.
Therefore, it would be beneficial to provide a semiconductor laser-based wavelength-stabilized source of high-power optical radiation that does not require an external FBG for the wavelength stabilization.